Biomarkers in upper Holocene Eastern North Sea and Wadden Sea sediments

Total extracts of sediment cores from five different stations in the North Sea and Wadden Sea were analysed for their biomarker composition. Only sediments of the Skagerrak contained significant amounts of marine biomarkers (mainly alkenones), other sites contained predominantly terrestrial biomarkers. Bioturbation in the Skagerrak is, however, far too high to determine sea surface temperature (SST) changes within short time intervals. These results indicate that biomarkers contained in these sediments are not useful to reconstruct climate fluctuations during the upper Holocene. High amounts of α-, β- and ω-hydroxy fatty acids as well as small amounts of α, β-dihydroxy fatty acids were released from the insoluble organic material of the sediments from the Wadden Sea station, indicating a significant input of the eelgrass Zostera marina. This was confirmed by microscopic observations. This is the first time the α,β-dihydroxy fatty acids have been found in a sediment core and they have proven to be potential biomarkers for these seagrass species.     

硫对海洋小球藻铜胁迫的影响研究

硫是小球藻(Chlorella sp.)生长的必需元素,影响着小球藻的生长代谢,也是其抗重金属胁迫机制中的重要元素之一.为了研究供硫对小球藻铜胁迫效应的影响,在实验条件下以海洋小球藻为目标,研究设置了正常供硫且无铜胁迫、正常供硫与缺硫条件下铜胁迫(铜浓度1.5mg.L-1)3个处理.结果表明,缺硫导致铜胁迫程度增强,小球藻生长受抑制程度比供硫胁迫组更大,而小球藻对铜的吸收更少.供硫处理组分泌的可溶性有机质显著高于缺硫处理组,培养液pH值下降程度低于缺硫处理组,说明供硫能够促进小球藻分泌有机质、合成含硫化合物,达到缓解铜胁迫的目的.     

Modelling suitable estuarine habitats for Zostera noltii, using Ecological Niche Factor Analysis and Bathymetric LiDAR

Predicting species distribution and habitat suitability is of considerable use in supporting the implementation of environmental legislation, protection and conservation of marine waters and ecosystem-based management. As other seagrasses, Zostera noltii has declined worldwide, mainly due to human pressures, such as eutrophication and habitat loss. In the case of the Basque Country (northern Spain), the species is present only in 3 out of 12 estuaries. From the literature, it is known that at least 6 of these estuaries were formerly vegetated by this seagrass. Consequently, efforts to monitor and restore (potential) habitats have been enhanced. Therefore, we aim: (i) to determine the main environmental variables explaining Zostera noltii distribution, within the Basque estuaries based upon the Oka estuary; (ii) to model habitat suitability for this species, as a wider applicable management-decision tool for seagrass restoration; and (iii) to assess the applicability and predicted accuracy of the model by using internal and external validation methods. For this purpose, Ecological Niche Factor Analysis (ENFA) has been used to model habitat suitability, based upon topographical variables, obtained from bathymetric Light Detection And Ranging (LiDAR); sediment characteristics variables; and hydrodynamic variables. The results obtained from the ecological factors of the ENFA (Marginality: 1.00; Specialization: 2.59) indicate that the species habitat differs considerably from the mean environmental conditions over the study area; likewise, that the species is restrictive in the selection of the range of conditions within which it dwells. The main environmental variables relating to the species distribution, in order of importance, are: mean grain size; redox potential; intertidal height; sediment sorting; slope of intertidal flat; percentage of gravels; and percentage of organic matter content. The model has a high predicted accuracy (Boyce index: 0.92). Model validation using an independent dataset in the Bidasoa estuary has shown the applicability but also the limitations in extrapolating the habitat suitability model to select suitable transplantation areas in other estuaries with similar morphological and biogeographical characteristics. ENFA-technique, applied with an accurate selection of environmental predictors, could be a promising tool for predicting seagrass habitat suitability which could assist on seagrass conservation and restoration programs worldwide.     

中国温带海域新发现较大面积(大于50ha)海草床:Ⅲ渤海兴城-觉华岛海域大面积海草床鳗草种群动力学及补充机制

鳗草(ZosteramarinaL.)广布于北半球温带浅海海域,其形成的鳗草床具有重要的生态价值。近些年来,我国黄渤海海域鳗草退化严重,较大面积、连续分布的海草床已经非常少见。在渤海兴城-觉华岛海域发现较大面积的海草床,可以作为渤海沿海海草床的典型代表。基于此,2018年5月、9月、11月和2019年3月对该海草床进行了初步调查,探究了渤海兴城-觉华岛海草床鳗草种群补充等生态特征,分析了海草床生境的主要威胁,并提出了对海草床进行有效保护和科学管理的相关建议。结果表明:渤海兴城-觉华岛海草床总面积为791.61ha,海草种类为鳗草和日本鳗草(Z.japonica),以鳗草为优势种,日本鳗草极少且呈斑块状分布;鳗草生物量在2018年5月达到最大值(1241.22—1632.64g/m2);鳗草叶片碳、氮、磷元素含量分别为35.35%—36.57%、1.89%—3.35%、0.14%—0.48%;鳗草海草床以无性繁殖为主要补充方式,有性繁殖补充比例平均仅为1.92%,明显低于国内其他鳗草草床,具有鲜明的独特性;该海草床主要受围填海、捕蛤、围网捕鱼等人类活动的严重影响,并致使海草床边缘区域呈现斑块化趋势。建议对这片珍贵的海草床加以保护和修复。     

2006年夏季渤海湾赤潮重点监控区的赤潮生物

2006年5月至8月渤海湾赤潮重点监控区共发生3次赤潮,引发赤潮的赤潮生物分别为赤潮异弯藻(Heterosigma akashiwo)、赤潮异弯藻-海洋卡盾藻(Heterosigma akashiwo- Chattonelta marina)、夜光藻(Noctiluca scintillans)。本文研究了赤潮生消过程中赤潮生物的变化和发展情况,揭示赤潮生物的生长特性及其危害,为赤潮的预警提供基础资料。     

大叶藻(Zostera marina L.)胚的结构和种子萌发过程的研究

以采自山东荣成褚岛桑沟湾南岸成熟的大叶藻种子为材料,研究了种子的外部形态特征、胚乳成分及胚的解剖结构,并初步了解了大叶藻种子的萌发过程。结果表明,大叶藻种子是单子叶有胚乳的种子,呈暗褐色,椭圆形或长圆形,种皮革质且有17～20条纵肋,胚乳丰厚坚硬,胚乳细胞被淀粉粒充满;胚弯曲,由胚根、胚轴、胚芽和子叶组成,子叶U形棒状,其弯曲部有一裂缝,胚芽位于裂缝处,胚轴较短,其下是两个对生的胚根,有中央维管束贯穿胚根、胚轴、胚芽和子叶。在子叶出土萌发的植物类型中,大叶藻种子萌发过程是罕见的。萌发初期,子叶优先生长突破种皮而长出地面,此后胚根才开始生长并产生不定根。对大叶藻种子结构和萌发过程的研究,为探讨大叶藻种子萌发和幼苗更新的限制因素提供了一定的理论依据。     

大叶藻种子萌发环境条件研究

大叶藻海草床的退化和恢复受到国内外学者的广泛关注,而大叶藻种子萌发则是恢复实践中的一项关键技术。为了提高大叶藻种子萌发率,本研究在实验室可控条件下,采用正交实验对影响大叶藻种子萌发的环境因素(盐度、温度、N/P营养盐浓度及p H)进行了优化,并在优化条件下进一步探究了光质类型、UV-B辐射、低温层积和划破种皮对大叶藻种子萌发和平均萌发时间的影响。结果表明:盐度12、温度10°C、N/P营养盐浓度960/60μmol/L、p H 6.2是大叶藻种子相对适宜的萌发条件组合;黑暗条件下大叶藻种子萌发率最高,为92%,不同类型光质照射不促进大叶藻种子萌发率的提高,但红光照射可在短期内加速种子萌发;在一定强度范围内,种子萌发率随UV-B辐射时长的增加而升高,每日辐射8h,处理8周后种子萌发率可达93%。划破种皮和低温层积均可显著提高大叶藻种子的萌发率并缩短平均萌发时间,经划破种皮处理后,2周内种子萌发率可提高至91%。     

Seasonal and Between-Substrate Variation in Mobile Epifaunal Community in a Multispecific Seagrass Bed of Otsuchi Bay, Japan

Abstract. A seagrass bed in Otsuchi Bay, northeastern Japan, consists of three seagrass species ( Zostera marina, Z. caulescens and Z. caespitosa ) that differ in morphology and phenology. We studied the mobile epifaunal community in the seagrass bed to examine (1) whether seasonal and between-substrate variation in the epifaunal community agrees with variation in seagrass abundance and morphological complexity, and (2) whether patterns of seasonal and between-substrate variation vary among epifaunal species. We collected mobile epifauna from each of Z. marina and Z. caulescens on 11 occasions between October 1995 and November 1996 (at 1 – 1.5 month intervals) using a hand-closing net. A total of 9 842 individuals of mobile epiphytic animals were collected and they were classified into 80 taxa. Abundance and species richness of the epifaunal community were high in summer to autumn and low in winter to spring, and diversity index and evenness were higher in Z. marina than Z. caulescens . However, patterns of seasonal and between-substrate variation in these parameters did not parallel those in seagrass abundance and complexity. Most of the dominant epifaunal species showed significant seasonal and between-substrate variation in abundance, although their patterns varied greatly among individual species. A cluster analysis recognized several distinct groups of animals showing similar seasonal and between-substrate variation. Our findings suggest that the observed variation in the epifaunal community is not determined by a single or some strong external factors but by complex interactions of multiple factors operating differently for each component species.     

黄渤海典型鳗草海草床重金属生态风险评估

为全面了解我国黄渤海鳗草(Zostera marina L.)床重金属污染水平, 本研究以大连林阳北海、葫芦岛兴城、唐山乐亭-曹妃甸和青岛湾四处鳗草床为研究对象。于夏季采集鳗草、海水和沉积物样品并分析其重金属(Cu、Zn、Pb和Cd)含量。以此分析海草的重金属富集特征, 并对比评估不同鳗草床重金属潜在生态风险。结果表明, 夏季四处鳗草床海水重金属含量由高到低依次为: Zn > Cu > Pb > Cd, 均低于国家一级水质标准; 对沉积物来说, 重金属含量由高到低依次为: Zn > Pb > Cu > Cd, 均低于国家一级沉积物质量标准。鳗草对重金属的富集因重金属种类和海草积累部位而异, 其地上组织对Cu、Zn、Cd的富集能力高于地下组织。研究区域海水中Cu、Zn、Pb和Cd潜在风险等级均处于低风险水平。而对沉积物而言, 葫芦岛兴城鳗草床Cd的潜在风险等级处于较高风险水平(E_i值为156.9)。唐山乐亭-曹妃甸和青岛湾鳗草床的地质累积指数(I_geo)由大到小依次为: Cd > Pb > Zn > Cu。综合所有元素的潜在生态风险指数(I_R), 葫芦岛兴城鳗草床的潜在生态风险值最高。     

中国温带海域新发现较大面积(大于0.5km2)海草床:Ⅱ声呐探 测技术在渤海唐山沿海海域发现中国面积最大的鳗草海草床

近些年来随着生境的破坏其分布面积急遽下降,较大面积连续分布的海草床已经非常少见。本研究首次将声呐探测技术应用到海草床时空分布特征的相关研究中,在河北唐山乐亭-曹妃甸沿海发现目前中国面积最大的鳗草(Zostera marina)海草床,海草床面积高达29.17 km~2,绘制了鳗草分布图和水深分布图,并对鳗草生物量和茎枝高度等基本生物学指标进行了调查。该发现极大丰富了中国海草数据库,并为鳗草的深入研究及保护提供了得天独厚的实验基地,也为周边海洋牧场的构建打下良好的基础。